1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device by a plasma etching process using argon (Ar) ions.
2. Description of the Related Art
In a prior art method for manufacturing a semiconductor device, a first conductive layer is formed on a semiconductor substrate. Then, a plasma etching process using Ar ions is performed upon the first conductive layer to remove natural oxide from the first conductive layer. Finally, a second conductive layer is formed by a sputtering process on the first conductive layer. This will be explained later in detail.
In the above-described semiconductor device, if a heating process at a temperature such as 840xc2x0 C. is carried out at a post stage, argon atoms immersed in the first conductive layer are moved to an interface between the first and second conductive layers. As a result, the contact characteristics between the first and second conductive layers are deteriorated. At worst, the second conductive layer is peeled from the first conductive layer, and therefore, the second conductive layer is electrically separated from the first conductive layer. This would degrade the performance of the semiconductor device.
Note that JP-A-4-10621 discloses a radio-frequency (RF) plasma etching process using halogen fluoride diluted by Ar gas for silicon nitride, and JP-A-11-243082 discloses an RF plasma etching process using a mixture of fluorine gas and Ar gas for silicon oxide. However, neither one suggests the expulsion of Ar atoms immersed into semiconductor devices.
It is an object of the present invention to expel Ar atoms from a semiconductor device to improve the contact characteristics between two conductive layers, one of the conductive layers being formed by a sputtering process.
According to the present invention, in a method for manufacturing a semiconductor device, a first conductive layer is formed on a semiconductor substrate. Then, a plasma etching process using Ar ions is performed upon the first conductive layer to remove natural oxide from the first conductive layer. Then, a heating process at a temperature higher than about 650xc2x0 C. is performed upon the first conductive layer to expel Ar atoms from the first conductive layer. Finally, a second conductive layer is formed by a sputtering process on the first conductive layer.